Understanding Isolates and Concurrency in Flutter

1. Introduction

Goal

The goal of this tutorial is to give you a firm grasp of Isolates and Concurrency in Flutter. By the end of this tutorial, you will understand how to use Isolates to prevent UI blocking when performing heavy operations.

What you will learn

• An understanding of Isolates and Concurrency in Flutter.
• How to use Isolates to run tasks in the background.
• Best practices when working with Isolates.

Prerequisites

• Basic knowledge of Flutter and Dart.
• Familiarity with asynchronous programming in Dart.

2. Step-by-Step Guide

What are Isolates?

In Dart and Flutter, all code runs on a single thread by default. Isolates are Dart's model for multithreading, though they work a bit differently than threads in other languages. An isolate has its own memory heap, ensuring that no isolate can access any other isolate's state.

How do Isolates enable Concurrency?

Isolates are independent workers that are similar to threads but don't share memory, communicating only via messages. They are helpful for performing work in the background and can help you achieve concurrency in your Flutter apps.

3. Code Examples

Example 1: Creating a new Isolate

Let's have a look at how you can create a new isolate:

import 'dart:isolate';

void main() {
  Isolate.spawn(isolateMethod, "Hello from the main thread");
}

void isolateMethod(String message) {
  print('Execution from new isolate: $message');
}

In this example, we're spawning a new isolate and passing a message to it.

Example 2: Communication between Isolates

Isolates communicate by sending each other messages. Here's how you can achieve this:

import 'dart:isolate';

void main() async {
  ReceivePort port = ReceivePort();

  Isolate.spawn(isolateMethod, port.sendPort);

  final sendPort = await port.first;

  final answer = new ReceivePort();

  sendPort.send(["Hello from main", answer.sendPort]);

  print(await answer.first);
}

void isolateMethod(SendPort port) {
  port.send("Hello from new isolate");
}

In this example, we're creating a new isolate and setting up a communication link between the main isolate and the new isolate.

4. Summary

In this tutorial, you've learned about Isolates and Concurrency in Flutter. You've learned how to create new isolates and how isolates can communicate with each other.

For further learning, you could explore how to handle errors in isolates, how to close isolates when they're not needed anymore, and how to use the compute function, a simple way to move a single function call to a new isolate.

5. Practice Exercises

Exercise 1

Create a new isolate and send a message to it. Print this message from the new isolate.

Exercise 2

Set up a communication link between two isolates and exchange messages.

Exercise 3

Create a new isolate, send a message to it, and receive a response.

For further practice, consider exploring how to use isolates for more complex tasks, such as downloading files or performing heavy computations.